1. Technical Field
The present invention relates generally to semiconductor manufacturing, and more particularly, to a method of selectively heating particular regions of a substrate without damaging surrounding regions.
2. Related Art
In the manufacture of semiconductor devices, a semiconductor substrate is often subjected to an ion implanting process to form heavily doped source-drain regions of CMOSFET devices. Subsequent to the ion implanting process, the substrate is exposed to high temperatures. This type of annealing process is necessary to restore the crystallinity of the substrate and electrically activate the doped ions implanted in the surface of the substrate. This is typically accomplished via a furnace, rapid thermal, or laser annealing process.
However, since the annealing process currently used heats the entire substrate, it is difficult to achieve optimal results for multiple dopant anneals since the heat cannot be focused exclusively on a desired area. In fact, when the substrate is exposed to high temperatures the profiles of surrounding doped shallow source-drain regions may become deformed, move or increase in depth in the substrate thereby degrading the device performance characteristics. Consequently, it is very difficult to form the shallow junctions necessary for high performance semiconductor devices using a conventional wafer annealing method.
Based on the above description, there is a need for a new method of selectively heating particular regions of a substrate without damaging surrounding regions. More particularly, there is a need for a method of forming and activating locally doped regions of a semiconductor substrate that will not damage the surrounding doped and activated regions.
The present invention provides a method of overcoming the above-identified problems of the related art by selectively activating certain doped regions of a semiconductor substrate using a laser, while protecting the surrounding doped and activated regions using a photolithographically defined reflective mask.
The first general aspect of the present invention provides a method for local activation comprising the steps of: providing a substrate having a first section and a second section, wherein the first section contains at least one doped and activated region; depositing a reflective mask over the first section to protect the at least one doped and activated region; implanting a dopant species in at least one region of the second section; and activating the dopant species. This aspect provides for a method of activating doped regions of a semiconductor device. Further, this aspect provides for the use of a reflective mask to prevent the destruction of underlaying doped and activated regions when the substrate is exposed to the activation process.
The second general aspect of the present invention provides a method for local activation of a semiconductor device including the steps of: depositing a reflective mask over a previously doped and activated first section of a substrate; implanting a dopant on a second section of the substrate; and activating the dopant of the second section. This aspect provides similar advantages as those described in the first aspect.
The third general aspect of the present invention provides for a reflective mask used to protect underlaying regions of a semiconductor substrate upon dopant activation of adjacent portions of the substrate. This aspect provides similar advantages as the first aspect.
The fourth general aspect of the present invention provides for a semiconductor device comprising: a substrate having a previously doped and activated first section, and a second section; a reflective mask over the first section to protect the first section from damage caused by further processing; and at least one inactivated doped region in the second section. This aspect provide for a device formed in accordance with the present invention.
The fifth general aspect of the present invention provides for a semi-transparent layer of reflective material, having a topography with varying thickness, to allow for the selective activation of a doped region. This aspect allows for the selective activation of particular regions to varying degrees.
The foregoing and other features and advantages of the invention will be apparent from the following more particular description of the preferred embodiments of the invention.